Current Biology
Volume 30, Issue 9, 4 May 2020, Pages 1762-1769.e5
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Report
Traction Forces Control Cell-Edge Dynamics and Mediate Distance Sensitivity during Cell Polarization

https://doi.org/10.1016/j.cub.2020.02.078Get rights and content
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Highlights

  • Traction forces correlate with the distance from the center to the edge of the cell

  • Analysis of edge and stress dynamics suggests that stress triggers edge retraction

  • Unlike traction stress, actin flow correlates with distance only during retraction

  • Simple model reproduces force-distance relationship

Summary

Traction forces are generated by cellular actin-myosin system and transmitted to the environment through adhesions. They are believed to drive cell motion, shape changes, and extracellular matrix remodeling [1, 2, 3]. However, most of the traction force analysis has been performed on stationary cells, investigating forces at the level of individual focal adhesions or linking them to static cell parameters, such as area and edge curvature [4, 5, 6, 7, 8, 9, 10]. It is not well understood how traction forces are related to shape changes and motion, e.g., forces were reported to either increase or drop prior to cell retraction [11, 12, 13, 14, 15]. Here, we analyze the dynamics of traction forces during the protrusion-retraction cycle of polarizing fish epidermal keratocytes and find that forces fluctuate together with the cycle, increasing during protrusion and reaching maximum at the beginning of retraction. We relate force dynamics to the recently discovered phenomenological rule [16] that governs cell-edge behavior during keratocyte polarization: both traction forces and probability of switch from protrusion to retraction increase with the distance from the cell center. Diminishing forces with cell contractility inhibitor leads to decreased edge fluctuations and abnormal polarization, although externally applied force can induce protrusion-retraction switch. These results suggest that forces mediate distance sensitivity of the edge dynamics and organize cell-edge behavior, leading to spontaneous polarization. Actin flow rate did not exhibit the same distance dependence as traction stress, arguing against its role in organizing edge dynamics. Finally, using a simple model of actin-myosin network, we show that force-distance relationship might be an emergent feature of such networks.

Keywords

cell polarization
cell migration
traction force microscopy
actin flow
cell adhesion
keratocytes
cell contractility

Cited by (0)

3

Present address: UMR S1255, Etablissement Français du Sang, rue Spielmann, Strasbourg 67000, France

4

These authors contributed equally

5

Lead Contact